US envoys were expected in the Pakistani capital on Saturday to kickstart a new round of peace negotiations with Iran, although Iranian state media said Tehran's representatives had no immediate plans to hold face-to-face talks.

Already in Islamabad, Iran's Foreign Minister Abbas Araghchi met Field Marshal Asim Munir, Pakistan's army chief and a key figure in the country's mediation efforts, and Prime Minister Shehbaz Sharif.

Aragchi, according to a statement from the foreign ministry, thanked Pakistan for its efforts to establish the ceasefire but also "explained our country's principled positions regarding the latest developments related to the ceasefire and the complete end of the imposed war against Iran".

Sealing a deal to end the Middle East war remains a thorny proposition, even as urgency mounts to reopen the Strait of Hormuz, a vital conduit for the world's oil and liquefied natural gas (LNG).

White House Press Secretary Karoline Leavitt said Steve Witkoff and Jared Kushner would leave for Pakistan on Saturday "to engage in talks... with representatives from the Iranian delegation".

"The Iranians reached out, as the president called on them to do, and asked for this in-person conversation," Leavitt said, adding that the talks would "hopefully move the ball forward towards a deal".

Leavitt said Vice President JD Vance, who led a first round of negotiations in Islamabad two weeks ago, would not be joining for the time being, but was on "standby to fly to Pakistan if necessary".

It remained unclear, however, whether the Iranian side would meet directly with the US envoys.